DFT Studies on a Metal Oxide@Graphene-Decorated D−π(1)–π(2)–A Novel Multi-Junction Light-Harvesting System for Efficient Dye-Sensitized Solar Cell Applications

[Image: see text] Graphene nanocomposites have emerged as potential photoanode materials for increased performance of the dye-sensitized solar cells (DSSCs) via charge transfer. Various metal-oxide-decorated graphene nanocomposites have widespread applications in energy devices, such as solar cells, fuel cells, batteries, sensors, electrocatalysis, and photocatalysis. However, the possible role of these composites in DSSC applications has largely remained unexplored. Herein, we studied a Sb(2)O(3)-decorated graphene–D−π(1)–π(2)–A sensitized TiO(2) nanocomposite (dye-(TiO(2))(9)/Sb(2)O(3)@GO) as a model multi-junction light-harvesting system and examined the impact of various π-bridges on the optical and photovoltaic properties of the push–pull dye system employed in this light-harvesting system. We have shown that by changing the spacer unit, the light sensitivity of nanocomposites can be varied from visible to near-infrared wavelengths. Furthermore, with the integration of metal-oxide-decorated graphene nanocomposites on D−π(1)–π(2)–A systems and D−π–A systems, composite photoelectrodes displayed better optical and photovoltaic characteristics with an enhanced absorption spectrum in the wavelength range of 800–1000 nm. The performance of the D−π(1)–π(2)–A system has been evaluated in terms of various photovoltaic parameters such as the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps, excited-state oxidation potential (E(dye)(*)), free energy of electron injection (G(inject)), total reorganization energy (λ(total)), and open-circuit voltage (V(oc)). This work throws light on the current trends and the future opportunities in graphene–metal oxide nanocomposite-based DSSCs for better harvesting of the solar spectrum and better performance of solar devices.